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CHAS. H. o’dONOGHUE. 
cells, and this observation has been confirmed by most inves- 
tigators since that time. The hypertrophy in Dasyurus 
occurs in quite a similar manner, and if the frequency of 
the occurrence of mitotic figures may be taken as an index of 
the formative growth of the gland, it would appear that the 
maximum growth activity is reached while the embryos are 
in the blastocyst stage (i.e. in Nos. 9 and 10). There 
are signs of mitoses in all the preparations of the gland during 
pregnancy, save perhaps the last. They are few in the early 
stages, but during the blastocyst stage they are fairly 
frequent. After the attachment of thefoetus they become fewer 
and fewer, ultimately disappearing altogether, and the large 
increase in size which occurs after this time is more or less of 
a mechanical nature. It is brought about by the increase in 
the size of the individual cells and the marked increase of 
the lumen in both acini and ducts. An examination of the 
sections of the gland of a domestic cat, in which there were 
young embryos present in the uteri, shows that a similar 
mechanical enlargement occurs after the growth of the 
gland. The actual formation of glandular tissue, as measured 
by the presence of mitotic figures in its epithelium, was at a 
standstill, and the gland possessed small, fully formed, single- 
layered acini. 
Winckler (50) has described a membrana propria of the 
glandular alveoli in the mammary gland in the form of a 
transparent non-cellular membrane. Kolossinikow (29), 
however, considers it to take the form of a network of 
anastomosing cells, an opinion also held by Heidenhain 
(22). It is described as a simple epithelial covering by 
Rauber (38) and by Jakowski (25) as consisting of several 
layers of anastomosing cells. My own observations confirm 
those of Sticker (45) and Bronha (loc. cit.), who deny its 
existence as a separate formation, and an examination of the 
forming, resting, and growing glands shows that in Dasyurus, 
at any rate, the so-called membrana propria is not an 
independent structure. It consists simply of conjunctive 
fibrillar cells from the stroma, which, during the enormous 
